This invention relates to a bicycle caliper brake assembly, and more particularly to such brake assembly provided with an auxiliary braking element adapted to work automatically in the event of an emergency.
In general, a bicycle caliper brake assembly has a pair of opposed caliper arms arranged so as to pivotally move in the opposite directions. One typical type of such brake assembly is known as a side pull type while the other typical type thereof is known as a center pull type, as taught by Page 373 of the "JAPANESE INDUSTRIAL STANDARD, Classification and Symbols of a Bicycle, 1975" edited in English by the Japanese Industrial Standard Association.
An example of a typical prior art side pull type caliper brake assembly is illustrated in FIG. 8 of the accompanying drawings for the convenience of explanation of the structure and arrangement of the conventional assembly.
Referring now to FIG. 8, the bicycle caliper brake assembly comprises a pair of curved caliper arms, that is the first arm 2 and the second arm 3, which are pivotally supported on a common horizontal support shaft 1 which is to be fixed to a bicycle frame. The first arm 2 has a shoe support section 4 and a connecting section 4'.
The shoe support section 4 extends to the lower right of the shaft 1 and has a right brake shoe 7 mounted to the lower end thereof. The connecting section 4' extends to the lower left of the shaft 1 and is connected at its free end 4a to an inner cable w1 of a known double type control cable W by means of a clamp 15. As is well known, the control cable W is connected at its non-illustrated remote end to a known brake lever (not shown).
The second arm 3 also has a shoe support section 5 and a connecting section 5'. The shoe support section 5 extends to the lower left of the shaft 1 and has a left brake shoe 8 mounted to the lower end thereof. The connecting section 5' extends to the upper left of the shaft 1 and is connected at its free end 5a to an outer cable w2 of the control cable W via an externally threaded sleeve 13 fixed to the lower end of the outer cable w2. The threaded sleeve 13 extends downward through a bore formed in the arm end 5a which is repositionable up and down on the sleeve 13.
An adjusting nut 14 is mounted on the threaded sleeve 13 to restrict the upward displacement of the arm end 5a to provide a selected vertical distance between the arm ends 5a, 4a.
The caliper brake assembly is normally held in its release position by means of a return spring 6 which has a central fixed portion 6a supported by the shaft 1 and a pair of resilient side legs 6b, 6c each extending downwardly from the central portion 6a and fixed at its lower end to the shoe support section 4, 5, respectively, Thus, the pair of caliper arms 2, 3 are always urged outwards by the return spring 6 but restricted from excessive outward displacement by the control cable W so that the brake shoes 7, 8 are properly spaced away from a bicycle wheel rim when the brake lever is in its rest position.
On the other hand, when the brake lever is operated to pull the cable w1, the vertical distance between the arm ends 5a, 4a is forcibly reduced to bring the arms 2, 3 into pivotal motion about the shaft 1 to bring the opposed brake shoes 7, 8 into braking contact with the bicycle wheel rim.
As will be apparent from the foregoing description, the conventional caliper brake assembly is not provided with any auxiliary braking means which works in the event of an emergency. For instance, when the inner cable w1 is unexpectedly broken or disengaged at its one end from the arm end 4a or at its remote end from the brake lever during cycling, the brake assembly does not work and, therefore, the cyclist finds it difficult to stop his bicycle. Such trouble in the brake assembly may cause a serious accident in a particular case.
It is, therefore, an object of the invention to provide an improved caliper brake assembly having an auxiliary braking element which works automatically in the event of an emergency.